By Yoo Jee-ho SEOUL, Aug. 25 (Yonhap) -- A foreign ministry official on Wednesday characterized the resumption of North Korea's denuclearization talks and the deadly sinking of a South Korean warship as "different" matters, suggesting some flexibility over restarting the nuclear negotiations Seoul conditioned to the North's apology. "Strictly speaking, the sinking of the Cheonan and our punitive measures against the North, and the resumption of the six-party talks are different in nature," the official told reporters on the condition of anonymity.

"The talks are related to denuclearization. Post-Cheonan measures are the security steps we took in the face of the grave matter. It'd be a stretch to establish a direct connection between the two."

The comments came just a day ahead of a Chinese envoy's scheduled trip to Seoul for talks expected to focus on restarting the six-party forum.

The six-party talks, involving the two Koreas, the United States, Russia, Japan and host China, began in 2003 with the purpose of ending Pyongyang's nuclear program in return for diplomatic and financial incentives. The negotiations have been suspended since the last session in December 2008, and nascent efforts for their resumption came to a halt with the sinking of the Cheonan in March.

A Seoul-led multinational investigation team concluded two months later that the North had torpedoed the warship, an accusation Pyongyang denies as "sheer fabrication." The U.N. Security Council "deplored" the sinking that claimed 46 lives, but did not explicitly hold the communist regime as responsible for the attack.

Seoul has demanded the North apologize for the incident as a precondition for the resumption of the talks. Its position is backed by Washington and Tokyo.

Wu Dawei, China's envoy to the six-party talks, is scheduled to visit Seoul from Thursday and meet his South Korean counterpart, Wi Sung-lac, and other officials for discussions on the stalled nuclear forum.

Wu was in North Korea last week for an unannounced visit. The envoy told Japanese media that North Korea expressed a willingness to have preliminary talks with the United States and have an informal meeting with other dialogue partners of the six-party setting.

The foreign ministry official stressed that the South's position that the North must first show "a clear willingness to denuclearize and take concrete actions" has not changed.

"North Korea must also take responsible action regarding the Cheonan sinking," he added. "After such a serious situation, North Korea can't just pretend nothing happened and push for restarting the talks," the official said.